title: Mono- and dicarbonyl-bridged tricyclic heterocyclic acceptors: synthesis and electronic properties.
abstract: A series of trialkylsilyl-substituted 2,2'-dithiophene, 4,4'-di-n-hexyl-2,2'-dithiophene, 5,5'-dithiazole, and 2,2'-diselenophene with carbonyl (2a-d) and α-dicarbonyl bridges (3a-d) were prepared from readily available dihalides, using double lithiation followed by trapping with N,N-dimethylcarbamoyl chloride or diethyl oxalate (or N,N-dimethylpiperazine-2,3-dione), respectively. Cyclic voltammetry reveals that the first half-wave reduction potentials for this series of compounds span a wide range, from -1.87 to -0.97 V vs the ferrocene/ferrocenium couple at 0 V (0.1 M (n)Bu(4)NPF(6) in THF). A significant increase of the first half-wave reduction potential (by 0.50-0.67 V) was observed on substitution of the monocarbonyl bridge with α-dicarbonyl. Adiabatic electron affinity (AEA, gas phase) trends determined via density functional theory (DFT) calculations are in good agreement with the electrochemical reduction potentials. UV-vis absorption spectra across the series show a weak absorption band in the visible range, corresponding to the HOMO→LUMO transition within a one-electron picture, followed by a more intense, high-energy transition(s). Single-crystal X-ray structural analyses reveal molecular packing features that balance the interplay of the presence of the bulky substituents, intermolecular π-stacking interactions, and S···O intermolecular contacts, all of which affect the DFT-evaluated intermolecular electronic couplings and effective charge-carrier masses for the crystals of the tricyclic cores.
authors.affiliation: School of Chemistry & Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, Georgia 30332-0400, United States. yulia.getmanenko@chemistry.gatech.edu
authors.forename: Yulia A
authors.initials: YA
authors.lastname: Getmanenko
authors.forename: Chad
authors.initials: C
authors.lastname: Risko
authors.forename: Paul
authors.initials: P
authors.lastname: Tongwa
authors.forename: Eung-Gun
authors.initials: EG
authors.lastname: Kim
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Bhupinder
authors.initials: B
authors.lastname: Sandhu
authors.forename: Tatiana
authors.initials: T
authors.lastname: Timofeeva
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Brédas
authors.forename: Seth R
authors.initials: SR
authors.lastname: Marder